Javanais is an element of Frenchslang where the extra syllable "av" is placed inside a word (an infix), between every consonant followed by a vowel, rendering it more incomprehensible. Some common words that are "javanised" are gros, meaning fat, which becomes gravos, bonjour, meaning hello, which becomes bavonjavour, and penible, meaning annoying, becomes pavenaviblave. Paris becomes "Pavaravis".

Around 1957, Boris Vian wrote a song La Java Javanaise. The lyrics are a didactical method to learn the javanais. Each verse is firstly articulated in regular French, then translated in slang. As the title suggests, the song is a Java, a parisian Dance craze. In 1962, Serge Gainsbourg wrote and sang a song called 'La Javanaise', a pun playing on Javanese dancing and the javanais style of speaking. The song heavily employs unaltered French words that naturally have the "av" sound; thus the lyrics resemble the word game of javanais.